In recent years, as development of information and communication devices have been advanced, capacities for signal lines in the devices have become insufficient. To solve this problem, copper electrical wiring of print substrates in the devices has been tried to be partly substituted with optical fibers or optical waveguides in order to utilize optical signals instead of electrical signals. Unlike the case of connecting between devices, in the inside of the devices, high density optical interconnection needs to be packed in a limited space, and thus, as in the case of ICs and multichip modules, photoelectric elements such as laser diodes and photodiodes are generally packed on surfaces of substrates, so that optical interconnection is laminated on the same substrates as those of electrical circuit boards.
Optical and electrical wiring substrates on which optical waveguides and electrical wiring are laminated on the same substrate are desirable structures because they enable high packaging densities and high-speed operations, as well as miniaturization. However, those substrates need a technique for converting optical paths in depthwise directions in order to optically connect optical axes of optical waveguides to photoelectric elements such as laser diodes and photodiodes.
As examples of such optical path conversion components, a method in which a microlens is used (see Patent Document 1) and a method in which an optical waveguide is bent into an L-shape for optical coupling have been developed (see Patent Document 2).